What are lymphocytes?

Cells mediate immune function, can survive for many years and circulate around blood and through lymphoid tissues (so in blood transfusion it is important to irradiate the blood to not get and WBC to acceptor). Two subtypes T and B cells B cells make Ab, T cells regulate immunity, help B cells and can kill virally infected cells 95% are found w/in lymphoid tissue, enter through lymph nodes or high endothelial venules and leave nodes through lymphatic vessels into blood Most are found in MALT (colon, tonsils, bronchus...)